Various types of vehicle-blocking barrier cable arrangements of the key-controlled type have been employed to control the entry of vehicles into parking enclosures, or the like; or to control the passage of vehicles to restricted areas within parks, recreational areas, etc. or to other locations where it is desired to prevent entry of unauthorized vehicles.
Prior to the device of the Linder U.S. Pat. No. 3,990,182, the locking devices employed with such barrier cables consisted largely of arrangements employing padlocks, or the like, requiring protection from the weather, and usually consisting of cumbersome and relatively expensive parts, being subject to rapid deterioration, being expensive to fabricate and install, being vulnerable to tampering and theft, being subject to mechanical failure, and being difficult to operate. Even the device of Linder '182, which successfully solved many of the prior problems, continues to rely on the presence of a padlock, and therefore has the problems inherent in the use of a padlock. Thus, there is a substantial need for a relatively simple and compact cable locking device which can be easily locked and unlocked by an authorized person but which cannot be readily unlocked without a proper key.
A preliminary search of the patent literature revealed the following prior U.S. Pats. of interest:
Michell, No. 1,331,778 PA1 Del Pesco, No. 3,435,642 PA1 Pender, No. 4,028,916 PA1 Mima, No. 4,033,160 PA1 Best, No. 4,055,973 PA1 Best, No. 4,075,878 PA1 Foster et al, No. 4,086,795